1. Field of the Invention
This invention relates to a rotating device suitable as a means for returning a drivable element to an original position, particularly to a barrel unit built in an electronic camera, a camera-fitted mobile phone or the like and capable of a shake correction against a camera shake, and an image sensing apparatus installed with such a barrel unit.
2. Description of the Related Art
In electronic cameras and the like, various shake correcting mechanisms have been adopted to suppress the disturbance of a photographed image due to the hand shake of a user. A so-called gimbal mechanism for rotatably supporting the entire barrel has been conventionally known as a shake correcting mechanism (see, for example, Japanese Unexamined Patent Publication No. H07-274056). Further, there has been also known a method for shifting a shake correcting lens disposed inside a barrel in such a direction as to cancel out the shake acting on a camera within a plane orthogonal to an optical axis (see, for example, Japanese Unexamined Patent Publication No. H05-107620).
In recent years, the miniaturization of electronic cameras has further advanced and, therefore, a shake correcting mechanism for a photographing optical system incorporated into an originally small digital equipment such as a small-size electronic camera and a camera-fitted mobile phone has been required to have a maximally compact construction. However, it is difficult to make a gimbal mechanism as disclosed in the first publication more compact. Further, the shake correcting lens needs to be miniaturized in the shake correcting mechanism disclosed in the second publication in the case of being installed into a small-size electronic camera or the like. It is difficult to precisely drive such a minute shake correcting lens, which leads to a problem of being difficult to perform a proper shake correction.
On the other hand, the applicant of the present application proposed a shake correcting method according to which an angled barrel for bending an optical axis of an incident light substantially at 90° is used and supported by means of one steel ball (pivot bearing portion) and two actuators, and a shake correction is performed by rotatably driving the entire angled barrel about two axes orthogonal to each other. Unlike the above gimbal mechanism, this shake correcting mechanism can be made considerably more compact.
In the shake correcting mechanism as above, it is necessary to return the barrel to a specified original position (centering) at the time of initial driving (at the time of an power-on operation). During the shake correction drive, it is also preferable to perform a similar centering operation at a suitable timing as a measure against the displacement of the barrel and a measure against a step-out in the case of using stepping motors or the like as actuators. Such a centering operation is desirably completed within as short a period as possible with the object of promptly making transition to the photographing operation. As a position detecting sensor for sensing the original position, a simplest sensing element is desirably used with the object of cost reduction and simplification of the construction of the apparatus. However, it is a reality at present that a rotating device (barrel unit) sufficiently good in terms of high-speed centering and lower cost has not been realized yet.